Method development and application for triazine herbicides analysis in water, soil and sediment samples from KwaZulu-Natal

Strategic use of crop residue biochars for removal of hazardous compounds in wastewater

Crop residues are affordable lignocellulosic waste in the world, and a large portion of the waste has been burned, releasing toxic pollutants into the environment. Since the crop residue is a carbon and ingredient rich material, it can be strategically used as a sorptive material for (in)organic pollutants in the wastewater after thermo-chemical valorization (i.e., biochar production). In this review, applications of crop residue biochars to adsorption of non-degradable synthetic dyes, antibiotics, herbicides, and inorganic heavy metals in wastewater were discussed. Properties (porosity, functional groups, heteroatom, and metal(oxide)s, etc.) and adsorption capacity relationships were comprehensively reviewed. The current challenges of crop residue biochars and guidelines for development of efficient adsorbents were also provided. In the last part, the future research directions for practical applications of the crop residue biochars in wastewater treatment plants have been suggested.

Methods optimization and application: Solid phase extraction, Ultrasonic extraction and Soxhlet extraction for the determination of antiretroviral drugs in river water, wastewater, sludge, soil and sediment

The continuous release of antiretroviral drugs into the environmental has resulted in the interest to assess their occurrence in various environmental matrices. Their presence has led to antiretroviral drugs being considered the pollutants of concern due to their possible alterations of the ecosystem as well as the antiviral resistance that may develop upon their unintentional consumption. Therefore, in this work, solid phase extraction (SPE), ultrasonic extraction (UE), Soxhlet extration (SE) and liquid chromatography coupled to photodiode array detector (LC-PDA) methods have been optimized and validated. They were then applied for the simultaneous determination of abacavir, nevirapine and efavirenz antiretroviral drugs in wastewater, river water, sludge, soil and sediments. The percentage recoveries ranged from 71% to 112% for SPE, 88 - 108% for SE and 61 - 104% for UE. Good precision with a relative standard deviation less than 20% in all compounds for all methods was obtained. The LODs and LOQs ranged between 0.68 and 0.77 µg/L and 2.1-2.4 µg/L for SPE; 0.8-0.9 µg/kg and 2.3-2.8 µg/kg for SE and 1.6-2.8 µg/kg and 4.9 - 7.0 µg/kg for UE, respectively. The concentrations ranged from <lod - 102 µg/L, <lod - 814 µg/L, and <lod - 6759 µg/L, <lod - 138 µg/g, <lod - 98.9 µg/g, in river water, wastewater, sludge, soil and sediment samples, respectively. Abacavir was dominant in water while efavirenz was dominant in soil/sediments. The results showed that SE is more sensitive and more accurate than UE, hence it can be recommended for routine analysis despite its longer extraction times. The percentage removal efficiency ranged from 44% to 87% for nevirapine, 6-53% for efavirenz, and 75-91% for abacavir which indicates that these compounds were not completely removed during the WWTP processes, hence they ended up in river waters.

Online Solid-Phase Extraction of Prometon and Prometryne Using MIL-101(Cr) as Sorbent before Gas Chromatographic Analysis: A Computational and Experimental Study and Comparison between Splitless and PTV Inlets

In this study, prometryne and prometon were extracted and preconcentrated from aqueous media using an online solid-phase extraction-thermal desorption method coupled with gas chromatography-flame ionization detector (GC-FID), equipped with two different inlets: split and programmable temperature vaporizer (PTV). For this purpose, the applicability of Tenax and a metal-organic framework were investigated as solid-phase sorbents. Several effective parameters on the extraction efficiency, such as the amount of sorbent, sample volume, sample pH and thermal desorption procedure were optimized. The analytical performance of the proposed methods showed an excellent linear dynamic range for prometon and prometryne (0.25-100 μg/L) and relative standard deviation less than 4.01%. Moreover, the detection limits below 0.20 and 0.35 μg/L were determined for prometon and prometryne, respectively. Additionally, molecular docking was applied to clarify the adsorption nature and binding energy of MIL-101(Cr) toward the studied analytes, which indicated an appropriate correlation between computational and experimental results. Finally, the proposed method was developed and validated for prometon and prometryne and successfully applied for their extraction from agricultural water, spiked with prometon and prometryne through its direct introduction into the GC inlet.

Reproductive toxicity due to herbicide exposure in freshwater organisms

Excessively used pesticides in agricultural areas are spilled into aquatic environments, wherein they are suspended or sedimented. Owing to climate change, herbicides are the fastest growing sector of the pesticide industry and are detected in surface water, groundwater, and sediments near agricultural areas. In freshwater, organisms, including mussels, snails, frogs, and fish, are exposed to various types and concentrations of herbicides. Invertebrates are sensitive to herbicide exposure because their defense systems are incomplete. At the top of the food chain in freshwater ecosystems, fish show high bioaccumulation of herbicides. Herbicide exposure causes reproductive toxicity and population declines in freshwater organisms and further contamination of fish used for consumption poses a risk to human health. In addition, it is important to understand how environmental factors are physiologically processed and assess their impacts on reproductive parameters, such as gonadosomatic index and steroid hormone levels. Zebrafish is a good model for examining the effects of herbicides such as atrazine and glyphosate on embryonic development in freshwater fish. This review describes the occurrence and role of herbicides in freshwater environments and their potential implications for the reproduction and embryonic development of freshwater organisms.

Optimization and application of QuEChERS and SPE methods followed by LC-PDA for the determination of triazines residues in fruits and vegetables from Pietermaritzburg local supermarkets

QuEChERS and solid phase extraction (SPE) methods were optimized and applied for the extraction of triazines in fruit and vegetables. These extraction methods are easy, effective, rugged and safe. Also, they have the ability to purify the extracts which leads to lower detection limits and higher recoveries of the analytes. The analysis were conducted using liquid chromatography coupled to photodiode array detector. The limits of detection and quantification ranged from 0.4 -1.4 µg/kg and 1.5 - 4.5 µg/kg, respectively, for QuEChERS and 0.3 - 1.8 µg/kg and 1.4 - 4.9 µg/kg respectively, for SPE. The recoveries ranged from 84 to 102% for QuEChERS and 76-119% for SPE, with relative standard deviation less than 20% for both methods. The fruits and vegetables analysed were apples, pears, carrots, potatoes, tomatoes, avocado, cucumber, spinach, bananas, and oranges. The concentrations detected ranged between 6 and 46 µg/kg in fruits and 4 - 84 µg/kg in vegetables. Simazine was detected in all fruits and vegetable samples except in pear, while terbutylazine was not detected in all samples analysed. Propazine and ametryn were only found in carrot while pear sample only had atrazine. The proposed methods proved to be sensitive and accurate indicating their applicability for detection and monitoring of the selected triazines in fruits and vegetables. However, QuEChERS can be recommended for routine analysis of these triazines due to its fewer extraction steps compared to SPE which is important for turn-around time.

Ultrasonic Followed by Solid Phase Extraction and Liquid Chromatography-Photodiode Array for Determination of Pharmaceutical Compounds in Sediment and Soil

This work reports on the method optimization and application for quantitative analysis of non-steroidal anti-inflammatory drugs and anti-epileptic drug in soil and sediment samples. The analytes were extracted by ultrasonic extraction followed by solid phase extraction and quantified using liquid chromatographic coupled with photodiode array. The sensitivity of the method was determined based on the limit of detection and the limit of quantification which ranged between (0.010-0.027 µg/kg) and (0.025-0.049 µg/kg), respectively. The %recoveries of the method ranged between 74% and 112%. The concentrations obtained in real samples ranged from 0.055 to 0.426 µg/kg in sediment and 0.044-0.567 µg/kg in soil samples. The highest concentration was found for diclofenac in soil samples.